咩叫rates of change in composite function models??

What is rates of change?
If Q is a quantity that is varying with time, we know that the derivative measures how fast Q is increasing or decreasing. Specifically, if we let t stand for time, then we know the following.
Rate of Change of a Quantity, Q = dQ/dt
If Q=1/t, the rate of change of W is given by dQ/dt= - 1/t^2

What is composite function models?
More generally, if we have two functions y=f(x) and z=g(y), we call z=g(f(x)) is a composite function.

Would you please give more information about the problems?